Laser electron beam x 30 Multi-Compton chamber system γ-ray cm Conceptual design in 2005 Snowmass X 5 at present Good progress During R&D From Conventional to Compton upgrade Junji Urakawa KILC12, Daegu, Korea GDE Source, 30min.

Experimental Results Polarization of positron beam 72+/-21%, predicted cal. value 77+/-10% e - spin in Iron e + beam spin non A(R)= +0.60± 0.25% A(L)= -1.18± 0.27% A(0)= -0.02± 0.25%

Polarized Positron Soure Compton Scheme An independent system based on the dedicated electron driver is a big advantage. Obtaining enough positron, is a technical challenge. ─ High intensity electron beam: Linac, Storage ring, ERL ─ High intensity photon beam: High power laser, optical cavity. ─ Stacking scheme: DR stacking, Pre-DR, etc.

Compton Ring A storage ring for electron driver:5.3nC, 6.2ns, 1ps, 1.8GeV, 0.6Jx5CP. Positron Ne+:2.0E+8/bunch is generated. 10 bunches are stacked on a same bucket. This process is repeated 10 times with 10ms interval for beam cooling. Finally, Ne+:2E+10 is obtained.

ERL ERL(Energy Recovery Linac) is employed as the dedicated electron driver. – 0.48nC, 18.5ns (54MHz) ~ 26mA, E=1.8GeV – N γ =2.3E+9 by 0.6 Jx5 CP, N e+ =2.0E+7/bunch By a semi-CW operation (50ms), 1000 times stacking in DR is performed and Ne+=2.0E+10 is obtained.

For Linac Compton Scheme, we can reuse 6GeV e-Linac with CO 2 laser cavity system. Also, the 6GeV Linac has to accelerate 10nC bunched beam with 132 bunches/pulse.

Finesse 5800, gain ~2000 was confirmed by generation of gamma-ray last year. Also, laser waist size was less than 15  m.

Laser System Development for Optical Cavity for Q-Beam project and ILC by Pump LD Fiber Amplification Burst Amp. By 100 times 30uJ/pulse 300mJ/pulse 300nJ/pulse 162.5MHz mode-locking 100mW Oscillator Then, amplified to 30W EO Modulation

12 Pulse laser storage in optical cavity and X-ray measurement in X-ray generation with 1000 enhancement by optical cavity Status ： 0.2mJ/pulse, target ： 10mJ/pulse X-ray measurement at 20 degree crossing angle Beam collision technique 43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray. X-ray Detector LUCX results Average power :40kW, 7psec(FWHM), next step :2MW Electron beam size 60  m in  Laser size:30  m in , target:electron beam size:10  m in , laser waist size:8  m in  MCP waveform background subtracted. Detected X-ray flux 1.2x10 5 Hz/~10%b.w. X-angle 20 deg.

2012/4/19HG We have developed the X-ray source based on inverse Compton scattering for X-ray Imaging. Cathode: Cs-Te Multi-bunch beam S-band accelerating tube (3m) Compton Chicane Q X-ray solenoid RF Gun UV: 3μJ/bunch e - beam B Q Q Collision point

Future plan for LUCX accelerator To downsize the accelerator, we have planed to install a 3.6cell rf-gun and a 12cell booster. – 3.6cell rf-gun Beam test has been started from Jan – 12cell booster This booster is making now. 2012/02/27OECD Global Science Forum14 1.6cell Rf-gun 3m accelerating tube 3.6cell Rf-gun 12cell booster

Beam size 10  m Change to head collision scheme to get another enhancement of 5 and to increase laser pulse duration ~30ps. Quantum project at STF

Q-Beam and cERL ‏ Energy : MeV Micro pulse rep.:162.5MHz, Current in macro pulse:10mA, Macro pulse rep: 5Hz Quantum-Beam project is a strategic R&D for X-ray source for various applications based on the SC linac. 1 st step: Pulsed X-ray generation with SC linac; It is carried out at KEK-STF, nd step: CW X-ray generation with SC ERL; It will be carried out at cERL-KEK, 2013~2014.

Laser Compton R&D A proof of principle experiment of the polarized positron generation by the inversed laser Compton has been done already at KEK-ATF. Demonstration of the system feasibility is the next milestone. – Demonstration of CR scheme : The experiment at ATF. – Demonstration of ERL scheme: 2 nd phase Q-beam and cERL at KEK.

Suggestion for future R&D 1.Should consider multi-laser pulses in a ring cavity which means the development of larger optical cavity for  -  collider. One optical cavity has about 10 laser pulses with 6.15 ns spacing and mirror cooling is necessary. 2. Positron bunch stacking into damping ring should be no beam lose. We have to invent new scheme, maybe asymmetric strong laser cooling. (Consider 1GeV stacking ring.) 3. Strong high reflectivity mirror should be developed for future high field physics and laser beam acceleration. 4. Redesign the scheme with head collision. How many optical cavities will be needed?

We have to assume 1GeV stacking ring (SR) with about 260m circumference. Then, we can reuse 5GeV heavy beam loading Linac to inject bunch train of 3x10 10 positrons/bunch into the damping ring within 63ms. Regarding Ring Compton since the period of 100 times positron bunch stacking is about 87  s, the cooling period of 3.2ms for Compton ring and SR is enough for stable operation of the ring. 20 times beam extraction from SR means it takes 63ms by 300Hz Linac operation. Of course, we have to construct 5Hz SC Linac with 63ms pulse duration and 1GeV acceleration. Regarding ERL Compton since we need 1000 times of the beam stacking, the period of 1000 times positron bunch stacking is about 2.5ms for ERL Compton. 1GeV SC Linac with 63ms pulse duration has 20 trains which consist of 132x1000 bunches train in 2.5ms with train spacing of 0.8ms for the bunch train extraction. The 0.8ms for SR is enough for the stable operation of the beam extraction operation. Then, we can reuse 300Hz Linac to accelerate and to inject into the damping ring within 63ms. Figure shows the timing structure in the 300Hz booster linac and in the 5Hz superconducting linac for SR regarding Ring and ERL Compton.

1GeV stacking ring with about 260m circumference is necessary for accumulation beam. Also, 5Hz superconducting Linac with 63ms pulse duration and 1GeV acceleration are needed for 100 times or 1000 times bunch stacking. Thanks ERL cavity technologies. For Ring Compton scheme; 100 times injection with 132 bunches/pulse into stacking ring. Then, we can reuse 5GeV 300Hz heavy beam loading Linac from the 1GeV stacking ring to inject 132 bunches/pulse with 3x10 10 electrons/bunch. For ERL Compton Scheme; 1000 times injection with 132 bunches/pulse into stacking ring. Then, we can reuse 5GeV 300Hz heavy beam loading Linac from the 1GeV stacking ring to inject 132 bunches/pulse with 3x10 10 electrons/bunch.